Reduced weight, wide bandwidth, and improved immunity from electromagnetic interference are some of the potential benefits of introducing photonics technology in advanced active-array radar antennas, for space-based systems technology in advanced active-array radar antennas, for space-based systems and wide-band applications. To help incorporate optoelectronic components into radar systems, and to complement component testing, Technology Service Corporation (TSC) proposes Radar Optoelectronic Systems Simulator (ROSS), a general physics-based photonics simulation package for UNIX platforms. The simulation software will combine programs developed at TSC, and existing programs from other sources. Several Prototype TSC laser simulation routines will be built, including a novel laser simulation program for transient signals in the presence of spontaneous emission noise. A library of TSC radar system simulation programs will be included. Driver routines to integrate relevant programs into a single versatile package will be designed. A top-level design for an X-Window graphical user interface will be provided.